The four-hour contest at the Superdome in New Orleans averaged 108.7 million viewers, New York-based Nielsen said today in a statement. The figures exclude a half-hour commercial-free delay when play stopped.

The drop ends seven years of rising viewership for the game, annually the most-watched U.S. TV event. The audience shrank by 2.1 million during the blackout, Nielsen said. The lopsided 28-6 score before play was suspended and a lack of a national following for the teams were factors, Doug Creutz, a Cowen & Co. analyst in San Francisco, wrote in an e-mail.

The Ravens, helped by Jacoby Jones’s 108-yard kickoff return to open the third quarter, held a 28-6 lead when many of the Superdome’s lights went out.

Once play resumed, the 49ers staged a comeback, scoring 17 points over 4 minutes, 10 seconds. As the score tightened, more viewers tuned into the game. The audience peaked in the fourth quarter, CBS said.

Last Chance

San Francisco had an opportunity to claim the lead in the game’s final minutes, reaching the Ravens’ 5-yard line before a fourth-down pass from quarterback Colin Kaepernick fell incomplete with 1:46 left.

CBS Corp. (CBS), owner of the most-watched TV network, rose 0.5 percent to $42.08 at 12:33 p.m. in New York. As of yesterday, the stock had climbed 10 percent this year.

Even without a record, CBS is poised to win the 2012-2013 TV season in total viewers and the marketer-targeted 18-to-49- year-old age group, the network’s first such victory in two decades. Nielsen reports weekly ratings today.

CBS, home to the drama “NCIS” and the comedy “Big Bang Theory,” is already the most-watched U.S. network, averaging 11.7 million total prime-time viewers a night since the season began in September. It was second in 18 to 49 as of Jan. 27.

Ad Rates

The network, which also streamed the game online, charged advertisers an average of $3.75 million for a 30-second Super Bowl commercial, 7.1 percent more than a year ago, according to industry researcher Kantar Media, a unit of WPP Plc. (WPP)

When the blackout occurred, the network used back-up power and never went off the air. With lead broadcasters Phil Simms and Jim Nantz without electricity in the press box, sideline reporters Steve Tasker and Solomon Wilcots handled initial commentary duties during the power failure. The cause of the shutdown is under investigation.

All commercial commitments for the Super Bowl broadcast, even after a power failure delayed the game for more than half an hour, were honored, the network said last night in an e- mailed statement. The company doesn’t expect to be financially affected by the blackout, said a person with knowledge of the situation who wasn’t authorized to talk.

“We utilized CBS’s back-up power and at no time did we leave the air,” Jennifer Sabatelle, a CBS Sports spokeswoman, said in the statement. The network “reported on the situation as a breaking news story, providing updates and reports while full power was being restored to the dome including our sets and broadcast booth.”